The use of high pressure fluid jet streams for cutting various materials is well known and it has been demonstrated that a high velocity stream of water can be used to work certain types of hard rock, steel and many other materials by subjecting the materials to relatively high velocity jet streams for cutting, fracturing or otherwise working the materials. Such high velocity fluid jet streams have usually been directed against the material being worked on in the form of either a pulsed or a continuous jet stream. For best control of the cutting action, continuous jet streams are preferred, although pulsed jets of high velocity fluid have been found useful in some instances where a continuous cutting stroke is not essential or not capable of achieving the cutting or fracturing effect desired.
High velocity fluid jet streams have been produced in the past with mechanical intensifiers. The known mechanical intensifiers generally employ hydraulic power driven pistons of large diameter directly connected to drive smaller pistons that deliver the high pressure fluid. Such known apparatus are plagued with all the attendant problems of sealing, cylinder and piston wear, and need for complex valving arrangements.